Interviewer: You have 2 minutes. Explain the JavaScript Event Loop to me.
My answer: Challenge accepted, let’s go! 🚀
🔸 Single-Threaded Execution:
JavaScript operates on a single-threaded model, meaning it can handle only one task at a time. The tasks are managed using the call stack, which executes functions one by one.
🔸 Call Stack:
Imagine the call stack as a stack of plates. Each time a function is called, a plate is added to the stack. Once the function completes, the plate is removed.
🔸 Web APIs:
For tasks like setTimeout, DOM events, or HTTP requests, JavaScript uses Web APIs provided by the browser. These tasks are processed outside the call stack.
🔸 Callback Queue:
Once an asynchronous task finishes, its callback moves to the callback queue. The event loop only pushes the callback to the stack once the stack is empty.
🔸 Event Loop:
The event loop acts as a gatekeeper, checking if the call stack is empty. When it is, it takes the first task from the callback queue and pushes it onto the stack.
🔸 Microtasks Queue:
In addition to the callback queue, there’s a microtasks queue for tasks like promises. Microtasks are processed before any other callbacks, giving them higher priority.
🔸 Priority Handling:
To summarize, the event loop checks the microtasks queue first, then moves on to the callback queue. This ensures critical tasks (e.g., promises) are executed before other callbacks.
And that’s the JavaScript Event Loop! 🔄
💡 Stay curious, keep learning, and keep sharing! 💻✨
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